[15] 3Sum

https://leetcode.com/problems/3sum/description/

• algorithms
• Medium (22.44%)
• Source Code: 15.3sum.py
• Total Accepted: 522.7K
• Total Submissions: 2.2M
• Testcase Example: '[-1,0,1,2,-1,-4]'

Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.

Note:

The solution set must not contain duplicate triplets.

Example:

Given array nums = [-1, 0, 1, 2, -1, -4],

A solution set is: [ [-1, 0, 1], [-1, -1, 2] ]

class Solution(object):
    def threeSum(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        result = []
        lenn = len(nums)
        if lenn < 3: return result

        nums.sort()
        # print('nums', nums)
        for i in range(0, lenn-2):
            if i > 0 and nums[i] == nums[i-1]: continue
            j, k = i+1, lenn-1
            while i < j < k:
                sm = nums[i] + nums[j] + nums[k]
                if sm == 0:
                    result.append([nums[i], nums[j], nums[k]])

                    k -= 1
                    j += 1
                    while k > j and nums[k+1] == nums[k]:
                        k -= 1
                    while j < k and nums[j-1] == nums[j]:
                        j += 1

                elif sm > 0:
                    k -= 1
                else:
                    j += 1

        return result
#
#
# arr = [-1,0,1,2,-1,-4]
#
# s = Solution()
# print s.threeSum(arr)